Method of making an electrical connection



Dec. 11, 1962 N. E. HOFFMAN METHOD OF MAKING AN ELECTRICAL CONNECTION 2 Sheets-Sheet 1 Filed Dec. 28, 1956 N m NF u m i N M R O N Dec. 11, 1962 N. E. HOFFMAN 3,067,489

METHOD OF MAKING AN ELECTRICAL CONNECTION Filed Dec. 28, 1956 2 Sheets-Sheet 2 IN V EN TOR.

N me E. HOFFM RN BY j mi w W "United States atet fifice 3367,48?) Patented Dec. 11, 1962 3,067,489 METHOD OF MAKING AN ELECTRICAL CONNECTION Norman E. Hoffman, Rutherford Heights, Pa., assignor t AMP Incorporated, Harrisburg, Pa. Filed Dec. 28, 1956, Ser. No. 631,344 1 Claim. (Cl. 29155.55)

The present invention comprises a continuation-in-part of my previous application, Serial No. 441,277, filed July 6, 1954, now Patent No. 2,965,147, for Crimping Methods and Apparatus.

The previously filed application teaches the advisability of crimping an electrical connector to a conductor in a manner whereby the entire periphery of the connector is deformed in cross section to simulate an isosceles triangle.

The present invention contemplates making the crimped connection by crimping the connector in two spatially disposed sections. Each of these sections is crimped simultaneously with a confined type of crimp.

Other objects and attainments of the present invention will become apparent to those skilled in the art upon a reading of the following detailed description when taken in conjunction with the drawings in which there is shown and described an illustrative embodiment of the invention; it is to be understood, however, that this embodiment is not intended to be exhaustive nor limiting of the invention but is given for purposes of illustration in order that others skilled in the art may fully understand the invention and the principles thereof and the manner of applying it in practical use so that they may modify it in various forms, each as may be best suited to the conditions of a particular use.

In the drawings:

FIGURE 1 is an exploded perspective View of an electrical connector and conductor prior to joining them together;

FIGURE 2 is an exploded perspective view similar to FIGURE 1 after the connection has been made;

FIGURE 3 is a cross sectional view taken IIIIII of FIGURE 1;

FIGURE 4 is a cross sectional view taken lVIV of FIGURE 2;

FIGURE 5 is a cross sectional view taken VV of FIGURE 4;

FIGURE 6 is an exploded perspective view of the dies usedin making the connection shown in FIGURE 2; and

FIGURES 7, 8, and 9 are views of the connector and dies during the crimping operation.

As shown in FIGURE 1, an electrical connector, generally designated 1%, is adapted to be secured to a conductor -12. The connector is comprised of a deformable metal ferrule 14, capable of receiving the conductor 12. As shown in FIGURE 3, the conductor 12 fits into the ferrule so that all of the strands of the conductor are contained within the ferrule. (The conductor may be either solid or stranded. FIGURES 5 and 7 through 9 show the conductor in solid cross section for ease of illustration.)

When the conductor is positioned centrally of the ferrule, crimping dies, as shown in FIGURE 6, are brought to bear upon the ferrule until the connector and conductor are cold forged into an intimate, metal-to-metal contact, as illustrated in FIGURES 4 and 5.

The dies employed in achieving this invention are known as confining dies, and the crimped connection is designated as a confined crimp. This is due to the relationship of parts wherein the entire outer periphery of the connector is engaged by the working surface of the dies, at least during the final stages of crimping, note FIGURE 9. This is in contrast to an unconfined crimp,

through through through e.g. the patent to Carlson, 2,359,083, showing crimping dies which merely bear upon opposite surfaces of the connector, while the intermediate surfaces of the connector do not engage the dies. Unconfined dies permit the connector and conductor to be radially extruded upon crimping. However when a connector is crimped within confined dies, the radial extrusion is prevented by peripheral confinement of the connector so that any extrusion of the connector and conductor is in a longitudinal direction.

The parent application, Serial No. 441,277, is directed toward a particular type of confining dies. The dies set forth in this application are designed to crimp the connector and conductor into a scalloped isosceles triangle as seen in cross section. The advantages of this type of crimped connection are set forth in the prior application.

The present invention employs confined dies which may be of the type that effect a scalloped isosceles triangle as set forth above. However, in its broader aspects the improvement contemplates making a pair of confined crimps along two spatially disposed parallel sections. The crimps are impressed simultaneously, preferably by one set of dies. These confined crimps cause longitudinal extrusion of metal from opposite directions into the area between the crimps. The internal stresses caused by the extruded metal from one crimped area meeting the extruded metal from the other crimped area, traveling in the opposite direction, cause a large increase in the tensile strength of the connection with only a slight increase in the required crimping thrust.

As shown in FIGURE 6, one embodiment of co-operating dies includes a ferrule die nest 20 and amale die "22': These dies are similar to the type set forth in the abovementioned application. Directing attention to the male die 22, the working surface of the die is divided into two sections 24, 26 and 24', 26. These sections are spatially disposed by intermediate recesses 28, 30. The recess 28 separates the working surfaces 24, 24' while the recess 30 separates the working surfaces 26, 26'.

As shown in FIGURES 7, 8, and 9, the die nest 20 and die 22 are constructed to prevent radial extrusion of the connector. Since the deformation of the connector is limited by the shape and dimensions of the working surfaces, all the extrusion of the metal takes place longitudinally of the wire.

The present invention accomplishes this phenomenon by spatially disposing two sets of working surfaces in each die. These working surfaces, when brought together in crimping relationship, each effect a confined type of crimp. Each crimp causes metal to be extruded out of the crimped area in a direction longitudinally of the axis of the wire. Since each deformed section extrudes metal in the direction of the other crimped section, there is a flow of metal from opposite directions into the area between the crimped sections. This results in an intermediate section of metal which has been coined under pressure. Furthermore, the intermediate section of metal so formed has a greater diameter than the sections immediately adjacent to it.

The preferred embodiment includes a die section with working surfaces of equal length and an intermediate recess of the same length. Thus as shown in FIGURE 5, the crimped areas 36, 38 are of equal width and also equal to the width of the section 40 between the crimps.

A typital electrical connector of the size includes an inside d'ameter of .454" and an outside diameter ranging from .540 to .598" depending on the type of connector. This will accommodate a solid wire of .325 in diameter, an AN wire .432 in diameter or a 19 standard wire .373" in diameter. Each of the crimped zones is .137" in axial length and the intermediate uncrimped zone is the same.

The present invention achieves a two fold gripping action. First, a keyed connection results between the crimped sections and the intermediate section. Secondly, stresses are locked in the central section which exert a force ag'ainst'the adjacent sections. These stresses operate in a direction toward each of the crimped sections to 'bind the crimped connection more tightly. The net result is to increase the tensile strength tremendously, with only a slight increase in the crimping pressure.

The above data show the operational characteristics of a crimped connection as set forth in this application .(designated Split) compared with a standard crimp (designated Single), as demonstrated on three different types of Wire secured to a connector. In each case a 30% crimp reduction was effected. The Single crimp required 8500 pounds thrust to accomplish this whereas the Split crimp required 9000 pounds or less than 6% additional thrust. This 6% additional investment netted an increase in tensile strength of 35.5% on 19 standard Wire, 41% on AN Wire, and 38% on solid (annealed) wire.

Changes in construction will occur to those skilled in the art and various apparently different modifications and embodiments may be made without departing from 4, the scope of the invention. The matter set forth in the foregoing description and accompanying drawings is offered by way of illustration only. The actual scope of the invention is intended to be defined in the following claim when viewed in its proper perspective against the prior art.

I claim:

The method of crimping a metallic ferrule onto a conductor including the steps of (1) placing the conductor within the ferrule, (2) confining a section of the entire periphery of the ferrule Within a crimping die set, (3) confining a second section of the entire periphery of the ferrule within a second similar die set, longitudinally spaced from the first die set a distance equal to the thickness of the die set, and (4) simultaneously crimping both sections of the ferrule by compacting the connector and conductor into a substantially solid mass by applying equal pressure to each die set so that metal is squeezed out from the crimped sections into the intermediate uncrimped portion, whereby the ferrule and conductor are longitudinally extruded from each section into the section between the die sets.

References Cited in the file .of this patent UNITED STATES PATENTS 1,911,775 Smith et al. -May 30, 1933 2,018,996 Christians *Oct. 29, 1935 2,276,140 Andren Mar. 10, 1942 2,359,084 Carlson Sept. 26, 1944 2,379,567 Buchanan July 3, 1945 2,396,913 Carlson Mar. 19, 1946 2,639,754 Macy May 26, 1953 2,704,358 Wells Mar. 15, 1955 2,758,491 Buchanan Aug. 14, 1956 2,965,147 Hoifman Dec. 20, 1960 

